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Author: Patrick Hofmann
Publisher: BoD – Books on Demand
ISBN: 3752884924
Category : Science
Languages : en
Pages : 166
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Book Description
This dissertation employs doping to investigate basic gallium nitride (GaN) crystal properties and to solve challenges of the hydride vapour phase epitaxy (HVPE) growth process. Whereas the first chapter is a short introduction to the history of the GaN single crystal growth, the 2nd chapter introduces to current crystal growth techniques, discusses properties of the GaN material system and the resulting influence on the applicable crystal growth techniques. HVPE, as a vapour phase epitaxy crystal growth method will be explained in greater detail, with focus on the used vertical reactor and its capabilities for doping. The 3rd chapter then focusses on point defects in GaN, specifically on intentionally introduced extrinsic point defects used for doping purposes, i.e. to achieve p-type, n-type or semi-insulating behaviour. Different dopants will be reviewed before the diffusion of point defects in a solid will be discussed. The in-situ introduction of iron, manganese, and carbon during crystal growth is employed in chapter 4 to compensate the unintentional doping (UID) of the GaN crystals, and therefore to achieve truly semi-insulating behaviour of the HVPE GaN. However the focus of this chapter lies on the characterisation of the pyroelectric coefficient (p), as semi-insulating properties are a necessary requirement for the applied Sharp-Garn measurement method. The creation of tensile stress due to in-situ silicon doping during GaN crystal growth is the topic of the 5th chapter. The tensile stress generation effect will be reproduced and the strain inside the crystal will be monitored ex-situ employing Raman spectroscopy. The n-type doping is achieved by using a vapour phase doping line and a process is developed to hinder the tensile strain generation effect. The 6th chapter concentrates on the delivery of the doping precursor via a solid state doping line, a newly developed doping method. Similar to chapter 5, the doping line is characterised carefully before the germanium doping is employed to the GaN growth. The focus lies on the homogeneity of the germanium doping and it is compared compared to the silicon doping and the vapour phase doping line. Benefits and drawbacks are discussed in conjunction with the obtained results. The germanium doping via solid state doping line is applied to the HVPE GaN growth process to measure accurately growth process related properties unique to the applied set of GaN growth parameters.
Author: Patrick Hofmann
Publisher: BoD – Books on Demand
ISBN: 3752884924
Category : Science
Languages : en
Pages : 166
Get Book Here
Book Description
This dissertation employs doping to investigate basic gallium nitride (GaN) crystal properties and to solve challenges of the hydride vapour phase epitaxy (HVPE) growth process. Whereas the first chapter is a short introduction to the history of the GaN single crystal growth, the 2nd chapter introduces to current crystal growth techniques, discusses properties of the GaN material system and the resulting influence on the applicable crystal growth techniques. HVPE, as a vapour phase epitaxy crystal growth method will be explained in greater detail, with focus on the used vertical reactor and its capabilities for doping. The 3rd chapter then focusses on point defects in GaN, specifically on intentionally introduced extrinsic point defects used for doping purposes, i.e. to achieve p-type, n-type or semi-insulating behaviour. Different dopants will be reviewed before the diffusion of point defects in a solid will be discussed. The in-situ introduction of iron, manganese, and carbon during crystal growth is employed in chapter 4 to compensate the unintentional doping (UID) of the GaN crystals, and therefore to achieve truly semi-insulating behaviour of the HVPE GaN. However the focus of this chapter lies on the characterisation of the pyroelectric coefficient (p), as semi-insulating properties are a necessary requirement for the applied Sharp-Garn measurement method. The creation of tensile stress due to in-situ silicon doping during GaN crystal growth is the topic of the 5th chapter. The tensile stress generation effect will be reproduced and the strain inside the crystal will be monitored ex-situ employing Raman spectroscopy. The n-type doping is achieved by using a vapour phase doping line and a process is developed to hinder the tensile strain generation effect. The 6th chapter concentrates on the delivery of the doping precursor via a solid state doping line, a newly developed doping method. Similar to chapter 5, the doping line is characterised carefully before the germanium doping is employed to the GaN growth. The focus lies on the homogeneity of the germanium doping and it is compared compared to the silicon doping and the vapour phase doping line. Benefits and drawbacks are discussed in conjunction with the obtained results. The germanium doping via solid state doping line is applied to the HVPE GaN growth process to measure accurately growth process related properties unique to the applied set of GaN growth parameters.
Author: Rico Hentschel
Publisher: BoD – Books on Demand
ISBN: 3752641762
Category : Science
Languages : en
Pages : 156
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Book Description
Efficient power conversion is essential to face the continuously increasing energy consumption of our society. GaN based vertical power field effect transistors provide excellent performance figures for power-conversion switches, due to their capability of handling high voltages and current densities with very low area consumption. This work focuses on a vertical trench gate metal oxide semiconductor field effect transistor (MOSFET) with conceptional advantages in a device fabrication preceded GaN epitaxy and enhancement mode characteristics. The functional layer stack comprises from the bottom an n+/n--drift/p-body/n+-source GaN layer sequence. Special attention is paid to the Mg doping of the p-GaN body layer, which is a complex topic by itself. Hydrogen passivation of magnesium plays an essential role, since only the active (hydrogen-free) Mg concentration determines the threshold voltage of the MOSFET and the blocking capability of the body diode. Fabrication specific challenges of the concept are related to the complex integration, formation of ohmic contacts to the functional layers, the specific implementation and processing scheme of the gate trench module and the lateral edge termination. The maximum electric field, which was achieved in the pn- junction of the body diode of the MOSFET is estimated to be around 2.1 MV/cm. From double-sweep transfer measurements with relatively small hysteresis, steep subthreshold slope and a threshold voltage of 3 - 4 V a reasonably good Al2O3/GaN interface quality is indicated. In the conductive state a channel mobility of around 80 - 100 cm2/Vs is estimated. This value is comparable to device with additional overgrowth of the channel. Further enhancement of the OFF-state and ON-state characteristics is expected for optimization of the device termination and the high-k/GaN interface of the vertical trench gate, respectively. From the obtained results and dependencies key figures of an area efficient and competitive device design with thick drift layer is extrapolated. Finally, an outlook is given and advancement possibilities as well as technological limits are discussed.
Author: Dirk Ehrentraut
Publisher: Springer Science & Business Media
ISBN: 3642048307
Category : Science
Languages : en
Pages : 337
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Book Description
This book discusses the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production.
Author: David J. Miller
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 131
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Book Description
Gallium nitride is an important material for the production of next-generation visible and near-UV optical devices, as well as for high temperature electronic amplifiers and circuits; however there has been no bulk method for the production of GaN substrates for device layer growth. Instead, thick GaN layers are heteroepitaxially deposited onto non-native substrates (usually sapphire) by one of two vapor phase epitaxy (VPE) techniques: MOVPE (metalorganic VPE) or HVPE (hydride VPE). Each method has its strengths and weaknesses: MOVPE has precise growth rate and layer thickness control but it is slow and expensive; HVPE is a low-cost method for high rate deposition of thick GaN, but it lacks the precise control and heterojunction layer growth required for device structures. Because of the large (14%) lattice mismatch, GaN grown on sapphire requires the prior deposition of a low temperature MOVPE nucleation layer using a second growth process in a separate deposition system. Here we present a novel hybrid VPE system incorporating elements of both techniques, allowing MOVPE and HVPE in a single growth run. In this way, a thick GaN layer can be produced directly on sapphire. GaN growth commences as small (50-100 nm diameter) coherent strained 3-dimensional islands which coalesce into a continuous film, after which 2-dimensional layer growth commences. The coalescence of islands imparts significant stress into the growing film, which increases with the film thickness until catastrophic breakage occurs, in-situ. Additionally, the mismatch in thermal expansion rates induces compressive stress upon cooling from the growth temperature of 1025°C. We demonstrate a growth technique that mitigates these stresses, by using a 2-step growth sequence: an initial high growth rate step resulting in a pitted but relaxed film, followed by a low growth rate smoothing layer. As a result, thick (> 50 [Mu]m) and freestanding films have been grown successfully. X-ray rocking curve linewidth of 105 arcseconds and 10K PL indicating no "yellow" emission indicate that the material quality is higher than that produced by conventional MOVPE. By further modifying the hybrid system to include a metallic Mn source, it is possible to grow a doped semi-insulating GaN template for use in high frequency electronics devices.
Author: Vaibhav Uday Chaudhari
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Book Description
It was also found that the polycrystalline nature is as a result of polycrystalline nature of LT-GaN grown on the InN template. It was also shown that formation of completely enclosed uniformly distributed nanovoids were very essential to grow crack free thick GaN which is highly textured in 0002 orientation. It was also shown that GaN grown was very high quality crystal free of Indium. GaN growth on Indium metal deposited on Silicon was also studied. Depending on growth mode and conditions GaN 40 micron thick film and 100nm x 5000nm GaN wafers were successfully grown in same reactor.
Author: A. Hangleiter
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 440
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Book Description
The Symposium on 'Nitrides and related wide band gap materials' at the 1998 Spring Meeting of the European Materials Research Society (E-MRS) in Strasbourg, France, was the third Symposium of its kind at an E-MRS meeting. Beginning in 1996, these Symposia enjoyed a steadily increasing popularity among European and international nitride researchers. Contributions covered the areas of hetero-epitaxy, bulk growth, structural, electrical and optical characterisation and device fabrication. Researchers from about 20 different countries presented their work at this symposium. Naturally, most papers were from within Europe (Germany, France, Russia and the United Kingdom) but there was also a remarkable number of contributions from overseas (USA, Japan and Korea.) For about 5 years now, semiconducting group-III nitrides have attracted an enormous level of research activity all over the world. Essentially this was triggered by the breakthroughs achieved by Shuji Nakamura and his group in Japan, who succeeded in making highly efficient blue, green and yellow light emitting diodes as well as violet laser diodes based on A1GaInN. Since then, intensive research related to material growth, device development, as well as to the fundamental properties of these materials is being carried out. The outstanding contribution of Shuji Nakamura to this field was underlined by his plenary lecture during this E-MRS meeting. He presented his most recent progress towards amber LED's and long-lived violet laser diodes.
Author: Alan Paul Gott
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Dirk Ehrentraut
Publisher: Springer
ISBN: 9783642048289
Category : Science
Languages : en
Pages : 326
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Book Description
This book discusses the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production.
Author: Donald T. Hawkins
Publisher: Springer
ISBN:
Category : Reference
Languages : en
Pages : 762
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Author: Robert David Armitage
Publisher:
ISBN:
Category :
Languages : en
Pages : 462
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